Dehydrated lignite and process of producing same



- ent Patented Feb. 23, 1926.

V UNITED STATES PATENT OFFICE.

EUGENE P. SCI-IOCH, OF AUSTIN, TEXAS.

DEHYDRATED LIGNITE AND PROCESS OF PRODUCING SAME.

No Drawing.

To all whom it may concern:

Be it known that I, EUGENE P. Sonoorr, a citizen of the United States, residing at Austin, in the county of Travis and State of Texas, have invented certain new and useful Improvements in Dehydrated Lignite and Processes of Producing Same; and

-I do hereby declare the following to be a while at the same time producing a superior product.

IVith these and other objects in view, the invention consists in the novel steps and combinations of steps constituting the process and in the novel dehydrated lump lignite fuel constituting the product, all as will be more fully hereinafter disclosed and particularly pointed out in the claims.

This invention constitutes an improvement over the disclosure of my co-pending application Serial No. 575,656, filed July 17, 1922, entitled Dehydrated lignite and process of producing the same, now Pat- Number 1,508,617 dated septembei 16, 1924, in that among other things, it enables one to leave a lesser quantity of oil in the finished product all as. will appear more fully hereinafter.

In order that the precise invention may be the more clearly understood, it is said Fresh lignite as obtained in the mines frequently contains say from 25% to 35% of moisture, which it loses when heated at 110 C. to constant weight. Heated above this temperature, to 300 C. it gives up still more moisture, and some carbon dioxide; and heated still higher it begins to yield tar, and combustible gases;

the deep-seated decomposition which it then undergoes involves an exothermic reaction so that the heating power of the products when used as a fuel is less than that of the original material and the decomposition thus entails an actual loss of heating power.

"When exposed to the air, raw lignite Application filed August 18, 1924. Serial No. 732,782.

gives up a large fraction of its moisture and disintegrates so extensively as to become mostly dust or fine particles. This same disintegration takes place 1n the fire when lignite is used as a fuel, and hence,

unless special grates are provided, much of the lignite drops unburned 'into the ash pit. l/Vhen heated in retorts or dryers to expel the moisture, lignite disintegrates entirely, producing dust or very small fragments. 6 The large amount of water in lignite and the fact that it disintegrates whenever it loses its water either in storage or during combustion, naturally affects its commercial value greatly, and hence improved processes for making a better form of fuel out of lignite have been and are being actively sought. The only process known to me or proposed prior to my invention for producing a better form of lump fuel from 7 lignite consists in ,retorting the material and briquetting the resulting powder. This requires 10% or more of a first class asphalt, coal tar pitch or other suitable carbona-i ceous binder, a mixing operation to impreg 8 pate the powderwith the binder, and then briquetting the material with strong presses. The difficulty of doing this economically and the high cost of the initial installation has retarded capitalists from en- 8 tering into this business. It results that the proper machinery, as well as the details of the whole procedure are today still in their experimental stages.

I have discovered, on the other hand, as 9 stated in my said prior application, that when fresh lump lignite is heated in a still while immersed in thin petroleum oil, such as gas oil or engine distillate, it gives up its moisture without forming any appreciable 9 amount of powder or small fragments. In fact, the original lumps remain intact, although they may have formed some cracks. Most of these cracks are very fine, while large parts of the pieces are entirely free 1 from cracks. This invention, however, is not limited to the use of the specific oil mentioned, for oils having a paraffin base, and oils having-an asphaltic base of all de 'grees of thickness can be used so long as 1 they are capable of coating the lignite, but I prefer a thin oil to a thick one for most purposes.

In carryingout this present improved process, I prefer to cover the lignite entirely 1 with oil and to use the lumps as they ordinarily come from the mine, when they range, say, in smallest dimensions from 1 inch to 5 inches, and in largest dimensions from 3 to 8 inches. The time required to raise the temperature of the mixture to say 250 C. or higher in the still is about two to three hours, depending upon the composition of the oil. The oil is then drained out of the still. An examination of this oilheated lignite if made at this stage would show that all the lumps retain their original form, and although the treated material is brittle, yet, most of the pieces are suiticiently firm to be handled withoutdisintegration. As compared with some of the same lignite which is air-dried simultaneously, the oil-dried lignite would further show a much smaller number of cracks, which do not gape open as wide as is the case in the air-dried lignite. Further, if some of the oil dried lignite were broken at this stage, the fragments would be relatively large, while the air-dried material is cracked so extensively that it separates readily into very small fragments, and even into dust particles.

So far as now stated, the procedure of this invention is, or may be, substantially the same as in my said co-pending application above mentioned.

In this present improvement, however, I further proceed as follows: After draining off the oil from the lignite, I treat the latter with steam, gas or other fluid in order to lessen the quantity of oil retained by the lignite. By proceeding in the manner disclosed, I am enabled to lessen the quantity of oil retained by the lignite without impairing its physical qualities above mentioned, down to even as low as five per cent.

In carrying out my present improved invention, it is preferable to select an oil which is composed of say, three fourths gas oil and one fourth ordinary commercial fuel oil. I have found one suitable mixture to have the following distillation range:

100 c. c. distilled from an En ler flask as per U. S. Bureau of Mines specification for testing petroleum :begins to distill at 200 (3.; amount distilled to 250 6., 5%; amount distilled to 275 (1, 25%; amount distilled to 300 0., 60%; amount distilled to 340 0., 84%; residue, 16%.

After treating the lignite as above stated and draining off this oil, I prefer to blow steam through the mass of the hot lignite, which steam has been superheated to a temperature of say 400 C. The steam blast is preferably continued for about thirty to forty-five minutes, during which time about 15 to 20 pounds of steam for each 100 pounds of lignite have been used. Theoil and steam vapors may be condensed and the accompanying oil recovered and used over again.

5% or 6% of oil, and in all cases less than 10% of oil, or less than the product disclosed in my said prior application.

After this treatment with steam, the hot lignite product is suitably cooled when it is ready for the market. This cooling may be conveniently effected by spraying cold water thereover.

It is well known that some coals called lignitcs contain more than 35% of moisture and some contain less than 25% of moisture, and some authorities classify some of the last-named lignitcs as sub-bituminous coal. But this process is applicable with greater or less efficiency to all such coals which have a relatively high water content and which disintegrate or slack on exposure to the air. This said invention is believed, however, to be the most efficient when applied to those lignitcs having a water content of from 20% to 40%.

Instead of using steam to lessen the amount of oil retained by the lignite in the foregoing procedure, I may use hot flue gases which contain no substantial amount of free oxygen, or I may use hot producer gas or other suitable agency capable of carrying the hydrocarbon vapors formed by the evaporation of the oil from the hot lignite.

From the foregoing, it will now be clear that this invention when broadly considered consists in bringing the lignite into intimate contact with a hydrocarbon oil; raising its temperature to remove a very large proportion of the water present in the lignite; draining off said oil; leaving a considerable proportion of oil amounting to, say from 10% to 20% of the weight of said lignite sticking to the latter; and then subjecting the drained lignite to the action of steam, or other suitable agent, which removes the more volatile constituents of the oil remaining and leaves sticking to the lignite only a small percentage of the original oil after draining.

This remaining portion of oil is found to consist of the highest boiling constituents of the oil employed; and I have discovered that a proportion of these remaining constituents of the oil as low as 5% serve as an etiicient agent in preserving the advantageous physical properties of the lignite above mentioned, and preventing the finished product from reabsorbing objectionable amounts of moisture. I have also discovered thatsa'id small remainder of oil effectually prevents the finished lignite product from decomposing or changing its advantageous physical properties above mentioned upon exposure to air for long periods of time.

It will further now be seen that this process can be carried out by 'simple'mecnanism, continuously; and that the recovered oil may be used over and over again, leaving its higher boiling constituents behind in each cycle, and thus becoming lighter and lighter; or if it is desired to employ an oil of I a substantially constant composition, its

high boiling constituents left behind may be added to it after each cycle.

I have still further discovered that the latent heat necessary for the evaporation of the high boiling constituents left on the lignite after draining can be made to come out of the hot lignite, and thus serve to cool the same as well as to economize fuel. This is accomplished by so selecting an oil that its largest portion will be distilled within or near the highest range of the temperature of the hot lignite. That is to say, if aparticular lignite has to be heated before draining to about 290 C. in order to expel the water present, then the distillation range of the oil given in the table above will be very advantageous; for a large proportion of its vapors will be generated at temperatures from 290 C. down to about 240 C.

Also I have discovered that the removal of the light oil constituents from the oil remainingon the drained lignite improves the burning qualities of the finished product, in thatavhen said vapors are present they tend to cause the lignite to burn in a more or less'flashy manner, while after said vapors are removed the product burns in a more 4 steady manner simulating some forms of coal. Especially is this the case when the high boiling constituents let t on the lignite has a flash point aboutQOO F.

It is obvious that those skilled in the art may vary the foregoing procedure as well as the product produced thereby without de parting from the spirit of the invention, and therefore I do not wish to be limited to the above disclosure except as may be required by the claims.

hat is claimed 1. The process comprises heating of treating lignite which the same in contact with a hydrocarbon oil to drive off the moisture present and to cause a portion of said oil to enter the lignite, removing the oil not absorbed by the material; and still further removing a portion of the absorbed oil.

3. The process of treating lignite which comprises coating the same with a hydrocarbon oil; heating the coated lignite to a temperature sufiicicnt to drive off a substantial portion of the moisture present; re moving any oil not absorbed by the lignite;

and still further removing a substantial portion of the absorbed oil.

3. The process of treating lignite which comprises coating the same in the form of lumps with a hydrocarbon oil; heating the coated lignite to a temperature sufiicient to drive ofl' a substantial portion of the moisture present but insufficient to destroy its lump-like form; removing any oil not absorbed by the lignite; and still further removing by vaporization a substantial portion of the absorbed oil..

4. The process of treating lignite which consists in coating lumps of the raw material with a hydrocarbon oil by immersing said lumps in said oil; heating the coated lumps to a temperature sufficient to dehydrate the same; draining off any oil not absorbed by said lumps; removing the surplus oil; and further removing by vaporization a substantial portion of said surplus oil.

5. The process of treating lignite which consists in coating lumps of the raw material with a hydrocarbon oil; heating the coated lumps to a temperature suflicient to drive oflf a substantial portion of the water present; draining off any surplus oil present; and still further removing a substantial portion of the oilremaining on the drained lignite by subjecting the same to a hot fluid.

6. The process of treating lignite which consists in coating lumps of the raw material with a hydrocarbon oil by covering said lumps with said oil; heating the coated lumps and oil to a temperature sufiicient to drive off a substantial portion of the water present; draining olf any surplus oil present from said lumps; and still further removing a substantial portion of the oil remaining on the drained lignite by subjecting the same to the action of steam.

7 The herein described new article of manufacture comprising lump lignite of the shape it comes from the mine in which is incorporated less than ten per cent of a hydrocarbon oil. p

' 8, The herein described new article of manufacture comprising dehydratedlump lignite of the shape it comes'from the mine in which is incorporated less than eight per cent by weight of a hydrocarbon oil.

9. The herein described new article of manufacture comprising lump lignite of the general shape it comes from the mine and in which is incorporated less than seven per cent of a hydrocarbon oil.

10. The herein'described new article of manufacture comprising dehydrated lump lignite of the general shape it comes from the mine in'which is incorporated less than six per cent by weight of a hydrocarbon oil, substantially as described.

11. The herein described new article of manufacture, the same consisting of dehydrated lumps of lignite of the shape they 10 it comes from the mine,

form and in which is incorporated less than 10% of a hydrocarbon oil.

13. The herein described new article of manufacture, the drated lump lignite of the shape it comes from the mine in which is incorporated a hydrocarbon oil having a flashing point higher than 200 F.

In testimony whereof I aflix my signature.

EUGENE P. SCHOCH.

same consisting of dehy- 15 

